Elastomer porous material and method of producing the same

ABSTRACT

In the elastomer porous material of the invention, when cells in a first observation region of a first cross section are observed at a certain magnification, cells having an aspect ratio a/b, wherein a represents the maximum diameter of each cell and b represents the length of the minor axis of that cell as measured in a direction orthogonal thereto, of 1.3 or less account for 70% or more of all cells in the first observation region, and, when cells in a second observation region of a second cross section orthogonal to the first cross section are observed at a certain magnification, cells having an aspect ratio a/b, wherein a represents the maximum diameter of each cell and b represents the length of the minor axis of that cell as measured in a direction orthogonal thereto, of 1.3 or less account for 70% or more of all cells in the second observation region.

TECHNICAL FIELD

The invention relates to an elastomer porous material such as a siliconeelastomer porous material, and to a method for producing the elastomerporous material. More particularly, the present invention relates to anelastomer porous material having substantially true spherical cells, andto a method for producing the elastomer porous material.

BACKGROUND ART

Silicone elastomer porous materials are used in a variety of fields; forexample, in components of image-forming devices (e.g., copying machinesand laser printers), including a developing roller, a toner-feedingroller, a transfer roller, and a cleaning roller. Also, siliconeelastomer porous materials are used in paper-sheet-feeding rollers ofcopying machines, various types of printers, and plotters, as well as infixing components (e.g., a fixing roller and a pressure roller).

Hitherto, porous materials have generally been produced by means offoaming action. In a technique for causing foaming action, a chemicalfoaming agent, a gas, or water is used as a foaming agent.

In most cases of production of a silicone elastomer porous material,such a foaming agent is also used. However, in conventional methods forproducing such a silicone elastomer porous material, curing of siliconerubber and foaming are performed in parallel, and thus the resultantporous material has cells (pores) which are not uniform in size; i.e.,their sizes considerably differ from one cell to another. In addition,difficulty is encountered in forming spherical cells having a smallsize.

In view of the foregoing, Patent Document 1 discloses a method forproducing a silicone elastomer porous material by freezing aroom-temperature-curable organopolysiloxane emulsion containing, forexample, an organopolysiloxane having a silanol group, a specificcross-linking agent, a curing catalyst, and an emulsifier, and dryingthe frozen emulsion by sublimation of water without thawing. However,this method also encounters difficulty in producing a porous materialhaving small cells of uniform size.

When a silicone elastomer porous material produced by use of a foamingagent is used in a fixing roller, since the porous material has largecells of non-uniform size, the fixing roller poses problems in that itexhibits inconsistent form upon heating, and, when torque is applied tothe fixing roller, the roller is likely to break due to failure toachieve uniform distribution of the torque. When a porous materialhaving large-sized cells is used in, for example, a pressure roller, thecontours of the cells may appear on a formed image. Thus, demand hasarisen for a silicone elastomer porous material having small cells ofuniform size.

The present applicant previously applied for a patent on a closed-cellsilicone elastomer porous material which is produced essentially from awater-in-oil emulsion containing water and a liquid silicone rubbermaterial that forms a silicone elastomer through curing (see PatentDocument 2).

However, on the basis of subsequent studies, the present inventors havefound that the thus-produced silicone elastomer porous material hascells attributed to the water-in-oil emulsion, as well as cellsattributed to bubbles entrained upon preparation of the water-in-oilemulsion, and thus the porous material is unsatisfactory in terms ofproperties (in particular, durability) required of a silicone elastomerporous material.

Patent Document 1: Japanese Patent Application Laid-Open (kokai) No.H06-287348

Patent Document 2: Japanese Patent Application Laid-Open (kokai) No.2005-206784

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In view of the foregoing, an object of the present invention is toprovide an elastomer porous material which is produced from an emulsion,and which has substantially true spherical cells. Another object of thepresent invention is to provide a method for producing the elastomerporous material.

Means for Solving the Problems

In a first mode of the present invention attaining the aforementionedobjects, there is provided an elastomer porous material, characterizedin that, when cells in a first observation region of a first crosssection are observed at a certain magnification, cells having an aspectratio a/b, wherein a represents the length of the major axis of theperimeter of each cell (hereinafter referred to as “maximum diameter”)and b represents the length of the minor axis of that cell as measuredin a direction orthogonal thereto, of 1.3 or less account for 700 ormore of all cells in the first observation region, and, when cells in asecond observation region of a second cross section orthogonal to thefirst cross section are observed at a certain magnification, cellshaving an aspect ratio a/b, wherein a represents the maximum diameter ofeach cell and b represents the length of the minor axis of that cell asmeasured in a direction orthogonal thereto, of 1.3 or less account for70% or more of all cells in the second observation region.

A second mode of the present invention is drawn to a specific embodimentof the elastomer porous material as described above, which is producedfrom an emulsion composition comprising, as a continuous phase, a liquidrubber material which forms an elastomer through curing.

A third mode of the present invention is drawn to a specific embodimentof the elastomer porous material as described above, wherein the liquidrubber material is a liquid silicone rubber material.

A fourth mode of the present invention is drawn to a specific embodimentof the elastomer porous material as described above, wherein, in thefirst or second observation region, cells having a diameter of 50 μm orless account for 50% or more of all cells.

A fifth mode of the present invention is drawn to a specific embodimentof the elastomer porous material as described above, wherein, in each ofthe first and second observation regions, cells having a shape factorSF1, which indicates the roundness of a circle and is represented by thefollowing formula:

$\begin{matrix}{{{SF}\; 1} = {\frac{\pi \; a^{2}}{4\; A} \times 100}} & \lbrack{F1}\rbrack\end{matrix}$

(wherein a represents the length of major axis of each cell, and Arepresents the area thereof), of 150 or less account for 80% or more ofall cells.

A sixth mode of the present invention is drawn to a specific embodimentof the elastomer porous material as described above, wherein, in thefirst observation region, cells having a shape factor SF2, whichindicates the remoteness from complete roundness and is represented bythe following formula:

$\begin{matrix}{{{SF}\; 2} = {\frac{P^{2}}{4\pi \; A} \times 100}} & \lbrack{F2}\rbrack\end{matrix}$

(wherein A represents the area of each cell, and P represents theperimeter length thereof), of 130 or less account for 80% or more of allcells.

A seventh mode of the present invention is drawn to a specificembodiment of the elastomer porous material as described above, wherein,in the second observation region, cells having a shape factor SF2, whichindicates the remoteness from complete roundness and is represented bythe following formula:

$\begin{matrix}{{{SF}\; 2} = {\frac{P^{2}}{4\pi \; A} \times 100}} & \lbrack{F3}\rbrack\end{matrix}$

(wherein A represents the area of each cell, and P represents theperimeter length thereof), of 130 or less account for 80% or more of allcells.

An eighth mode of the present invention is drawn to a specificembodiment of the elastomer porous material as described above, whichexhibits a porosity of 30% or more and has 200 or more cells per mm² asobserved in a cross section.

In a ninth mode of the present invention, there is provided a rollmember characterized by comprising the elastomer porous material asrecited in any of the first to eighth modes.

In a tenth mode of the present invention, there is provided a fixingmember characterized by comprising the elastomer porous material asrecited in any of the first to eighth modes.

In an eleventh mode of the present invention, there is provided a methodfor producing an elastomer porous material, characterized in that themethod comprises preparing, under reduced pressure, an emulsioncomposition comprising, as a continuous phase, a liquid rubber materialwhich forms an elastomer through curing; and curing the emulsioncomposition while removing a dispersion phase, to thereby produce anelastomer porous material.

A twelfth mode of the present invention is drawn to a specificembodiment of the elastomer porous material production method asdescribed above, wherein the liquid rubber material is a liquid siliconerubber material.

A thirteenth mode of the present invention is drawn to a specificembodiment of the elastomer porous material production method asdescribed above, wherein the emulsion composition is a water-in-oilemulsion composition comprising a liquid silicone rubber material, asilicone oil material having interfacial activity, and water.

A fourteenth mode of the present invention is drawn to a specificembodiment of the elastomer porous material production method asdescribed above, which produces an elastomer porous material wherein,when cells in a first observation region of a first cross section areobserved at a certain magnification, cells having an aspect ratio a/b,wherein a represents the maximum diameter of each cell and b representsthe length of the minor axis of that cell as measured in a directionorthogonal thereto, of 1.3 or less account for 70% or more of all cellsin the first observation region, and, when cells in a second observationregion of a second cross section orthogonal to the first cross sectionare observed at a certain magnification, cells having an aspect ratioa/b, wherein a represents the maximum diameter of each cell and brepresents the length of the minor axis of that cell as measured in adirection orthogonal thereto, of 1.3 or less account for 70% or more ofall cells in the second observation region.

A fifteenth mode of the present invention is drawn to a specificembodiment of the elastomer porous material production method asdescribed above, which produces an elastomer porous material wherein, inthe first or second observation region, cells having a diameter of 50 μmor less account for 50% or more of all cells.

A sixteenth mode of the present invention is drawn to a specificembodiment of the elastomer porous material production method asdescribed above, which produces an elastomer porous material wherein, ineach of the first and second observation regions, cells having a shapefactor SF1, which indicates the roundness of a circle and is representedby the following formula:

$\begin{matrix}{{{SF}\; 1} = {\frac{\pi \; a^{2}}{4\; A} \times 100}} & \lbrack{F4}\rbrack\end{matrix}$

(wherein a represents the length of major axis of each cell, and Arepresents the area thereof), of 150 or less account for 80% or more ofall cells.

A seventeenth mode of the present invention is drawn to a specificembodiment of the elastomer porous material production method asdescribed above, which produces an elastomer porous material wherein, inthe first observation region, cells having a shape factor SF2, whichindicates the remoteness from complete roundness and is represented bythe following formula:

$\begin{matrix}{{{SF}\; 2} = {\frac{P^{2}}{4\; \pi \; A} \times 100}} & \lbrack{F5}\rbrack\end{matrix}$

(wherein A represents the area of each cell, and P represents theperimeter length thereof), of 130 or less account for 80% or more of allcells.

An eighteenth mode of the present invention is drawn to a specificembodiment of the elastomer porous material production method asdescribed above, which produces an elastomer porous material wherein, inthe second observation region, cells having a shape factor SF2, whichindicates the remoteness from complete roundness and is represented bythe following formula:

$\begin{matrix}{{{SF}\; 2} = {\frac{P^{2}}{4\; \pi \; A} \times 100}} & \lbrack{F6}\rbrack\end{matrix}$

(wherein A represents the area each cell, and P represents the perimeterlength thereof), of 130 or less account for 80% or more of all cells.

EFFECTS OF THE INVENTION

According to the present invention, there can be provided an elastomerporous material having substantially true spherical and fine cells andexhibiting excellent durability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an SEM photograph of a radial cross section and a firstobservation region in Example 1.

FIG. 2 shows an SEM photograph of a longitudinal cross section and asecond observation region in Example 1.

FIG. 3 shows an SEM photograph of a radial cross section and a firstobservation region in Example 2.

FIG. 4 shows an SEM photograph of a longitudinal cross section and asecond observation region in Example 2.

FIG. 5 shows an SEM photograph of a radial cross section and a firstobservation region in Example 3.

FIG. 6 shows an SEM photograph of a longitudinal cross section and asecond observation region in Example 3.

FIG. 7 shows an SEM photograph of a radial cross section and a firstobservation region in Comparative Example 1.

FIG. 8 shows an SEM photograph of a longitudinal cross section and asecond observation region in Comparative Example 1.

FIG. 9 shows an SEM photograph of a radial cross section and a firstobservation region in Comparative Example 2.

FIG. 10 shows an SEM photograph of a longitudinal cross section and asecond observation region in Comparative Example 2.

FIG. 11 shows an SEM photograph of a radial cross section and a firstobservation region in Comparative Example 3.

FIG. 12 shows an SEM photograph of a longitudinal cross section and asecond observation region in Comparative Example 3

FIG. 13 is a graph showing SF1 distribution in the first observationregion in Example 1.

FIG. 14 is a graph showing SF1 distribution in the second observationregion in Example 1.

FIG. 15 is a graph showing SF1 distribution in the first observationregion in Example 2.

FIG. 16 is a graph showing SF1 distribution in the second observationregion in Example 2.

FIG. 17 is a graph showing SF1 distribution in the first observationregion in Example 3.

FIG. 18 is a graph showing SF1 distribution in the second observationregion in Example 3.

FIG. 19 is a graph showing SF1 distribution in the first observationregion in Comparative Example 1.

FIG. 20 is a graph showing SF1 distribution in the second observationregion in Comparative Example 1.

FIG. 21 is a graph showing SF1 distribution in the first observationregion in Comparative Example 2.

FIG. 22 is a graph showing SF1 distribution in the second observationregion in Comparative Example 2.

FIG. 23 is a graph showing SF1 distribution in the first observationregion in Comparative Example 3.

FIG. 24 is a graph showing SF1 distribution in the second observationregion in Comparative Example 3.

FIG. 25 is a graph showing SF2 distribution in the first observationregion in Example 1.

FIG. 26 is a graph showing SF2 distribution in the second observationregion in Example 1.

FIG. 27 is a graph showing SF2 distribution in the first observationregion in Example 2.

FIG. 28 is a graph showing SF2 distribution in the second observationregion in Example 2.

FIG. 29 is a graph showing SF2 distribution in the first observationregion in Example 3.

FIG. 30 is a graph showing SF2 distribution in the second observationregion in Example 3.

FIG. 31 is a graph showing SF2 distribution in the first observationregion in Comparative Example 1.

FIG. 32 is a graph showing SF2 distribution in the second observationregion in Comparative Example 1.

FIG. 33 is a graph showing SF2 distribution in the first observationregion in Comparative Example 2.

FIG. 34 is a graph showing SF2 distribution in the second observation inComparative Example 2.

FIG. 35 is a graph showing SF2 distribution in the first observationregion in Comparative Example 3.

FIG. 36 is a graph showing SF2 distribution in the second observationregion in Comparative Example 3.

FIG. 37 is a schematic representation of the internal structure of abelt fixing apparatus employed in Test Example 3.

DESCRIPTION OF REFERENCE NUMERALS

-   10: Belt fixing apparatus-   21: Fixing roller-   22: Pressure roller-   23: Heating roller-   24: Heat source-   25: Fixing belt

BEST MODES FOR CARRYING OUT THE INVENTION

The elastomer porous material of the present invention is formed of anelastomer matrix and has numerous fine cells of substantially truespherical form distributed in the matrix.

Examples of the elastomer forming the matrix include silicone, urethane,chloroprene, ethylene-propylene copolymer (EPM), ethylene-propyleneterpolymer (EPDM), styrene rubber (SBR), nitrile rubber (NBR), polyesterelastomer, polyether elastomer, polyolefin elastomer, andepichlorohydrin rubber.

The elastomer porous material of the present invention is produced froman emulsion composition containing, as a continuous phase, a liquidrubber material which forms an elastomer. Specifically, the elastomerporous material is produced through the following procedure: the liquidrubber material (i.e., the continuous phase of the emulsion composition)is cured while the composition is maintained in an emulsion state, tothereby form an elastomer matrix, and subsequently the dispersion phaseis removed to form cells. The thus-formed cells present in the porousmaterial are substantially independent of one another. When the emulsioncomposition is prepared under reduced pressure so as to remove bubblescontained in the composition, the resultant porous material has onlycells formed by removal of the dispersion phase; i.e., the porousmaterial has substantially true spherical cells.

More specifically, the elastomer porous material having onlysubstantially true spherical cells is produced by removing cellsattributed to bubbles entrained in the emulsion composition. Most of thecells attributed to bubbles entrained in the emulsion composition have adiameter falling outside the range of the normal distribution of that ofcells attributed to the emulsion (e.g., a diameter of 50 to 60 μm). Whenthe cells attributed to such bubbles are precisely observed, the cellsare not in a true spherical form, but in a considerably flattened form.The present inventors have found that such considerable flattening ofthe cells, which may occur upon curing of the elastomer, causesdeterioration of properties (in particular, durability) of the elastomerporous material.

The elastomer porous material of the present invention can be confirmedto have only substantially true spherical cells by observing not onecertain cross section, but two orthogonal cross sections. Cellsconfirmed to be in a true circular form in the two orthogonal crosssections are also in a true circular form in another cross sectionorthogonal to these two cross sections.

In the present invention, cells observed in an observation cross sectionare confirmed to have a true circular form by determining that cellshaving an aspect ratio a/b, wherein a represents the maximum diameter ofeach cell and b represents the length of the minor axis of that cell asmeasured in a direction orthogonal thereto, of 1.3 or less account for70% or more of all cells in the observation region.

Specifically, in the elastomer porous material of the present invention,when cells in a first observation region of a first cross section areobserved at a certain magnification, cells having an aspect ratio a/b,wherein a represents the maximum diameter of each cell and b representsthe length of the minor axis of that cell as measured in a directionorthogonal thereto, of 1.3 or less account for 70% or more of all cellsin the first observation region, and, when cells in a second observationregion of a second cross section orthogonal to the first cross sectionare observed at a certain magnification, cells having an aspect ratioa/b, wherein a represents the maximum diameter of each cell and brepresents the length of the minor axis of that cell as measured in adirection orthogonal thereto, of 1.3 or less account for 70% or more ofall cells in the second observation region.

For determination of the aspect ratio, the two orthogonal cross sectionsare observed under an SEM, and each of the first and second observationregions is determined so that, for example, 40 to 80 cells are observedin the region. The aspect ratio a/b is determined by measuring thelength of major axis a of each cell representing its maximum diameter ofeach cell and the length b of the miner axis of that cell in a directionorthogonal thereto. Whether or not the cells in each of the observationregions satisfy the aforementioned requirements are determined on thebasis of the thus-obtained aspect ratio a/b.

Measurement of the length of major axis a and the length b of each cellmay be carried out through analysis of SEM image data input into acomputer by means of, for example, image analysis software.

Each of the first and second observation regions may be determined sothat, for example, about 40 to about 80 cells are present in theobservation region. Each of the observation regions may be the entirefield of view of SEM, or a certain region in the field of view.

As described in the previous patent application by the present applicant(Japanese Patent Application Laid-Open (kokai) No. 2005-206784), whencells are observed in a cross section, and cells satisfying therequirement represented by the below-described relation (A) or (B)account for 50% of all cells in the cross section, the cells areregarded as being in a true spherical form. However, this isinsufficient to indicate that the cells are in a true spherical form,since the cells are observed in only one cross section. The requirementrepresented by the below-described relation (B) corresponds to theaspect ratio employed in the present invention, and “0.5” shown inrelation (B) corresponds to an aspect ratio of 1.5. In the presentinvention, cells are observed in two orthogonal cross sections, andcells satisfying more stringent requirements than the requirementsrepresented by these relations are regarded as being in a true sphericalform.

(A): 0≦(m−n)/m≦0.5

(B): 0≦(m−n)/n≦0.5

(wherein m represents the length of major axis of a cell, and nrepresents the length of minor axis of the cell).

Also, the elastomer porous material of the present invention can beconfirmed to have substantially true spherical cells by determiningthat, in each of the first and second observation regions, cells havinga shape factor SF1—which indicates the roundness of a circle and isrepresented by the following formula in terms of the length of majoraxis a of each cell and the area A thereof—of 150 or less account for80% or more of all cells.

$\begin{matrix}{{{SF}\; 1} = {\frac{\pi \; a^{2}}{4\; A} \times 100}} & \lbrack{F7}\rbrack\end{matrix}$

Furthermore, the elastomer porous material of the present invention canbe confirmed to have substantially true spherical cells having smoothcircumferential surfaces with no irregularities by determining that, inthe first or second observation region, cells having a shape factorSF2—which indicates the remoteness from complete roundness and isrepresented by the following formula in terms of the area A of each celland the perimeter length P thereof—of 130 or less account for 80% ormore of all cells.

$\begin{matrix}{{{SF}\; 2} = {\frac{P^{2}}{4\; \pi \; A} \times 100}} & \lbrack{F8}\rbrack\end{matrix}$

When the aforementioned requirement (in relation to the shape factorSF2) is satisfied in any one of the first and second observationregions, it is enough to confirm that the elastomer porous material ofthe present invention has the aforementioned cells. However, therequirement may be satisfied in both the first and second observationregions.

Similar to the case of the aspect ratio, the shape factor SF1 or SF2 maybe determined through analysis of SEM image data input into a computerby means of, for example, image analysis software.

In the entirety of the elastomer porous material of the presentinvention, cells of uniform size are distributed uniformly. Therefore,observation of any cross section of the porous material provides resultssimilar to those as described above.

The elastomer porous material of the present invention has numerous veryfine cells which are densely distributed. Therefore, the number of cellsper unit area in the elastomer porous material greatly differs from thatin a conventional porous material produced through, for example,chemical foaming and having a porosity comparable to that of theelastomer porous material. The elastomer porous material of the presentinvention exhibits a porosity of, for example, 30% or more, preferably40% or more. In the elastomer porous material, the number of cells permm² is 200 or more, preferably 1,000 or more, more preferably 2,000 ormore.

Next will be described the elastomer porous material of the presentinvention and a production method therefor by taking, as an example, thecase of a silicone elastomer porous material.

The silicone elastomer porous material may be basically produced from awater-in-oil emulsion which contains a liquid silicone rubber materialthat forms a silicone elastomer through curing, and contains, as adispersion phase, water or a mixture of water and an aqueous solvent(e.g., alcohol). In this case, the liquid silicone rubber material(preferably, a liquid silicone rubber material having low viscosity) andwater may be thoroughly stirred under reduced pressure to form anemulsion, which may be immediately followed by heating for curing.

The silicone elastomer porous material of the present invention may besuitably produced from a water-in-oil emulsion which contains a liquidsilicone rubber material that forms a silicone elastomer through curing,water, and a silicone oil material having interfacial activity, andwhich is produced under reduced pressure.

No particular limitation is imposed on the liquid silicone rubbermaterial, so long as it forms a silicone elastomer through curing underheating. However, the liquid silicone rubber material employed ispreferably a so-called addition-reaction-curable liquid silicone rubbermaterial.

As described above, the elastomer porous material of the presentinvention has substantially true spherical cells. For production of theelastomer porous material, an emulsion composition must be preparedunder reduced pressure. As used herein, “preparation of an emulsioncomposition under reduced pressure” refers to the case where a processof preparing an emulsion through mixing and stirring of raw materials iscarried out under reduced pressure. Thus, even when an emulsioncomposition prepared at ambient pressure is subjected to degassing underreduced pressure, satisfactory effects are not obtained.

In the present invention, the liquid silicone rubber material employedmay be a commercially available one. For example, in the case of acommercially available addition-reaction-curable liquid silicone rubbermaterial, an unsaturated-aliphatic-group-containing polysiloxane and anactive-hydrogen-containing polysiloxane—which form the silicone rubbermaterial—are provided in separate packages, and a curing catalystrequired for curing both the polysiloxanes, which will be described indetail hereinbelow, is included in theunsaturated-aliphatic-group-containing polysiloxane package. Needless tosay, two or more liquid silicone rubber materials may be employed incombination.

The silicone oil material having interfacial activity serves as adispersion stabilizer for stably dispersing water in an emulsion. Thus,the silicone oil material having interfacial activity exhibits affinityfor both water and the liquid silicone rubber material.

Needless to say, in the aforementioned water-in-oil emulsion, water isdispersed in the form of particles (droplets) as a discontinuous phase(dispersed phase). As described in detail hereinbelow, the diameter ofwater particles substantially determines the diameter of cells (pores)of the silicone elastomer porous material of the present invention.

From the viewpoint of production of a water-in-oil emulsion exhibitingparticularly excellent water dispersion stability, preferably, thesilicone oil material having interfacial activity and water are employedin amounts of 0.2 to 10 parts by weight and 10 to 250 parts by weight,respectively, on the basis of 100 parts by weight of the liquid siliconerubber material. When such an emulsion exhibiting excellent waterdispersion stability is employed, a good porous material can be furtherreliably produced. Needless to say, two or more silicone oil materialshaving interfacial activity may be employed in combination.

When a liquid rubber material other than silicone is employed, theemulsion composition may be an emulsion containing, as a continuousphase, the liquid rubber material and, as a dispersed phase, a solventwhich can be phase-separated from the continuous phase, and optionallycontaining a surfactant or a substance having interfacial activity.

The elastomer porous material of the present invention may contain, inconsideration of the intended use thereof, a variety of additives.Examples of such an additive include a colorant (e.g., a pigment or adye), a conductivity-imparting material (e.g., carbon black or metalpowder), and a filler (e.g., silica).

The emulsion composition employed in the present invention may beproduced through various methods. For example, a water-in-oil emulsioncomposition containing a silicone elastomer may be generally produced bymixing a liquid silicone rubber material, a silicone oil material havinginterfacial activity, and water, and optionally an additive underreduced pressure, and by thoroughly stirring the resultant mixture. Forpreparation of the emulsion composition, no particular limitation isimposed on the order of addition of the respective materials, as well asthe method for mixing the materials, and the respective materials may beadded sequentially, or mixtures each containing a plurality of materialsmay be mixed together.

As used herein, “reduced pressure” refers to, for example, −30 kPa orless, preferably −60 kPa or less (lower limit: about −100 kPa).

Instead of mixing/stirring under reduced pressure, the respective rawmaterials may be degassed in advance, and then the materials may bestirred so that they are not exposed to a gas (e.g., air), to therebyprepare an emulsion.

For production of the elastomer porous material from the emulsioncomposition, the emulsion composition is subjected to primary heating(for curing) in the presence of an optional curing catalyst so thatcomponents of the composition are not evaporated, and subsequently theresultant composition is subjected to secondary heating for liquidremoval and complete curing.

For production of the silicone elastomer porous material, firstly, theemulsion composition is subjected to primary heating. The primaryheating is preferably carried out at 130° C. or lower for heating andcuring the liquid silicone rubber material without evaporation of watercontained in the emulsion composition. The primary heating temperatureis generally 80° C. or higher, and the heating time is generally about 5minutes to about 60 minutes. Through this primary heating, the liquidsilicone rubber material is cured, and water particles remain in thecured rubber material in the form of being dispersed in the emulsion.The silicone rubber material is cured to such an extent that it canresist expansion force upon evaporation of water by secondary heatingdescribed below. Secondary heating is carried out for removing waterfrom the cured silicone rubber material containing water particles. Thesecondary heating is preferably carried out at 70° C. to 300° C. Whenthe heating temperature is lower than 70° C., removal of water requiresa long period of time, whereas when the heating temperature exceeds 300°C., the cured silicone rubber material may be impaired. When the heatingtemperature is 70° C. to 300° C., removal of water (through evaporation)is completed by heating for 1 to 24 hours. Through this secondaryheating, water is evaporated and removed, and eventual curing of thesilicone rubber material is achieved. After removal of water throughevaporation, cells having a diameter almost equal to that of waterparticles are formed in the cured silicone rubber material (siliconeelastomer).

Thus, the elastomer porous material of the present invention can beproduced from the emulsion composition without involving foaming action(e.g., chemical foaming). The dispersed phase (e.g., water particles)contained in the emulsion composition remains in the elastomer curedthrough the primary heating, and only evaporates upon the secondaryheating.

The silicone elastomer porous material of the present invention can beemployed in a variety of fields. For example, the porous material can beemployed in components of image-forming devices (e.g., copying machinesand laser printers), including a developing roller, a toner-feedingroller, a transfer roller, and a cleaning roller. Also, the siliconeelastomer porous material can be employed in paper-sheet-feeding rollersof copying machines, various types of printers, and plotters, as well asin fixing components (e.g., a fixing roller and a pressure roller). Allof these rollers have basically the same structure, in which an elasticlayer formed of the silicone elastomer porous material of the presentinvention is provided around a core bar. The thickness of the elasticlayer, which may vary depending on the type of the roller, is generallyabout 0.1 mm to about 15 mm, and the length of the elastic layer isgenerally up to 400 mm. The outer diameter of the core bar, which mayalso vary depending on the type of the roller, is generally about 5 mmto about 50 mm.

EXAMPLES Example 1

As described below, a water-in-oil emulsion composition was prepared bycarrying out mixing and stirring under reduced pressure (−98 kPa) in areduced-pressure stirring apparatus.

A filler (5 parts by weight) and a silicone oil having interfacialactivity (5 parts by weight) were added to and mixed with liquidsilicone rubber (trade name: DY35-7002, obtained from Dow Corning TorayCo., Ltd.) (100 parts by weight) serving as a liquid silicone rubbermaterial, and the mixture was stirred. Subsequently, water (140 parts byweight) was gradually added to the resultant mixture under stirring, tothereby prepare a water-in-oil emulsion composition.

The resultant emulsion was added to a die containing an iron core barhaving a length of a surface on which rubber is applied (hereinafter maybe referred to as a “rubber surface length”) of 310 mm and an outerdiameter φ of 20 mm, and heating (primary heating) was carried out at130° C. for 40 minutes, to thereby form a molded product. The moldedproduct (porous material precursor) was subjected to heating (secondaryheating) in an electric furnace at 200° C. for six hours, to therebyremove water. Thereafter, polishing was carried out, to thereby producea roller having an outer diameter φ of 35 mm and a hardness (Asker C) of40°.

Example 2

As described below, a water-in-oil emulsion composition was prepared bycarrying out mixing and stirring under reduced pressure (−60 kPa) in areduced-pressure stirring apparatus.

A filler (5 parts by weight) and a silicone oil having interfacialactivity (5 parts by weight) were added to and mixed with liquidsilicone rubber (trade name: DY35-7002, obtained from Dow Corning TorayCo., Ltd.) (100 parts by weight) serving as a liquid silicone rubbermaterial, and the mixture was stirred. Subsequently, water (140 parts byweight) was gradually added to the resultant mixture under stirring, tothereby prepare a water-in-oil emulsion composition.

Subsequent processes were carried out in a manner similar to that ofExample 1, to thereby produce a roller having an outer diameter φ of 35mm and a hardness (Asker C) of 40°.

Example 3

As described below, a water-in-oil emulsion composition was prepared bycarrying out mixing and stirring under reduced pressure (−30 kPa) in areduced-pressure stirring apparatus.

A filler (5 parts by weight) and a silicone oil having interfacialactivity (5 parts by weight) were added to and mixed with liquidsilicone rubber (trade name: DY35-7002, obtained from Dow Corning TorayCo., Ltd.) (100 parts by weight) serving as a liquid silicone rubbermaterial, and the mixture was stirred under reduced pressure (−30 kPa).Subsequently, water (140 parts by weight) was gradually added to theresultant mixture under stirring, to thereby prepare a water-in-oilemulsion composition.

Subsequent processes were carried out in a manner similar to that ofExample 1, to thereby produce a roller having an outer diameter φ of 35mm and a hardness (Asker C) of 40°.

Comparative Example 1

In Comparative Example 1, a roller having an outer diameter φ of 35 mmand a hardness (Asker C) of 40° was produced from a silicone elastomerporous material (produced by kneading Silicone Rubber KE-951U (productof Shin-Etsu Chemical Co., Ltd.) with a vulcanizing agent compatibletherewith and a chemical foaming agent, followed by foaming).

Comparative Example 2

A filler (5 parts by weight) and a silicone oil having interfacialactivity (5 parts by weight) were mixed with liquid silicone rubber(trade name: DY35-7002, obtained from Dow Corning Toray Co., Ltd.) (100parts by weight) serving as a liquid silicone rubber material, and themixture was stirred by means of a hand mixer. Subsequently, water (140parts by weight) was gradually added to the resultant mixture understirring, to thereby prepare a water-in-oil emulsion composition.

The resultant emulsion was defoamed in a pressure reducer, to therebyremove air contained in the emulsion. Subsequently, the emulsion wasadded to a die containing an iron core bar having a rubber surfacelength of 310 mm and an outer diameter of 20 mm, and heating (primaryheating) was carried out at 130° C. for 40 minutes, to thereby form amolded product. The molded product (porous material precursor) wassubjected to heating (secondary heating) in an electric furnace at 200°C. for six hours, to thereby remove water. Thereafter, polishing wascarried out, to thereby produce a roller having an outer diameter φ of35 mm and a hardness (Acker C) of 20°.

Comparative Example 3

As described below, a water-in-oil emulsion composition was prepared bycarrying out mixing and stirring under reduced pressure (−20 kPa) in areduced-pressure stirring apparatus.

A filler (5 parts by weight) and a silicone oil having interfacialactivity (5 parts by weight) were added to and mixed with liquidsilicone rubber (trade name: DY35-7002, obtained from Dow Corning TorayCo., Ltd.) (100 parts by weight) serving as a liquid silicone rubbermaterial, and the mixture was stirred. Subsequently, water (140 parts byweight) was gradually added to the resultant mixture under stirring, tothereby prepare a water-in-oil emulsion composition.

Subsequent processes were carried out in a manner similar to that ofComparative Example 2, to thereby produce a roller having an outerdiameter φ of 35 mm and a hardness (Asker C) of 40°.

Test Example 1

Each of the rollers of Examples 1 to 3 and Comparative Examples 1 to 3was cut, in the vicinity of the center in an axial direction, in aradial direction and in a longitudinal direction orthogonal thereto.Each of the resultant cross sections was observed under an electronmicroscope (JSM 5600, product of JEOL Ltd.), and an image of the crosssection including 40 to 80 cells was obtained (magnification: ×1,000 forExamples, ×100 for Comparative Examples). A certain rectangular regionincluding cells whose entirety can be observed was determined in each ofthe cross-sectional images (a first observation region for the radialcross-sectional image and a second observation region for thelongitudinal cross-sectional image). Cells included in the rectangularregion (all cells on the boundary line were included in the region) weresubjected to the below-described measurements. In this test, the firstobservation region was determined in the radial cross section, and thesecond observation region was determined in the longitudinal crosssection. However, the first and second observation regions are notlimited thereto, and may be determined in any orthogonal cross sections.

FIGS. 1 to 12 show SEM photographs of radial cross sections and firstobservation regions thereof, and SEM photographs of longitudinal crosssections and second observation regions thereof in Examples 1 to 3 andComparative Examples 1 to 3.

The data of each cross-sectional image were input into Macrosoft lenaraf200 operated in Microsoft Excel. A reference length was determined, andthe circumference of each cell included in each observation region wastraced, to thereby select points corresponding the contour of the cell.Aspect ratio, SF1, and SF2 were calculated through the below-describedmethods. The results are shown in Table 1.

<Aspect Ratio>

For each cell, about 20 points were chosen on the perimeter thereof. Onthe basis of the thus-chosen points, the maximum diameter of each cell(length of major axis) a and the length b of minor axis orthogonalthereto were determined, to thereby calculate the aspect ratio a/b ofthe cell.

<SF1>

For each cell, about 20 points were chosen on the perimeter thereof. Onthe basis of the thus-chosen points, the maximum diameter of each cell(length of major axis) a was determined, and the area of the cell wasdetermined by means of the software. SF1 was calculated from thethus-determined values. FIGS. 13 to 24 show histograms of SF1 inExamples 1 to 3 and Comparative Examples 1 to 3.

<SF2>

For each cell, about 20 points were chosen on the perimeter thereof. Onthe basis of the thus-chosen points, the perimeter length and area ofthe cell were determined by means of the software. SF2 was calculatedfrom the thus-determined values. FIGS. 25 to 36 show histograms of SF2in Examples 1 to 3 and Comparative Examples 1 to 3.

Test Example 2

Each of the cross-sectional images obtained in Test Example 1 wasprinted out, and the inside of each cell included in the first andsecond observation regions was painted with a black marker pen. Thethus-painted image was scanned with a scanner, and the diameter andnumber of cells were determined by means of V10 for Windows (registeredtrademark) 95 (product of Toyobo Co., Ltd.). Definition was adjusted to150 so that cells were well recognized by the software. Porosity wascalculated on the basis of the ratio of the area of cells (average celldiameter×the number of cells) to that of the image. The number of cellsper mm² was calculated by dividing the number of cells in theobservation region by the area of the observation region. The resultsare shown in Table 1.

TABLE 1 Example 1 Example 2 Example 3 First Second First Second FirstSecond observation observation observation observation observationobservation region region region region region region Number of cellscounted 47 63 45 40 74 43 Aspect ratio Mean 1.16 1.16 1.22 1.27 1.261.21 Cells of 1.3 or less [%] 89 87 80 70 72 84 Cells of 1.2 or less [%]77 73 60 44 50 63 Cells of 1.1 or less [%] 36 37 33 23 22 35 SF1 Mean121.82 119.72 139.18 141.16 138.11 131.87 Cells of 150 or less [%] 94 9083 80 81 85 Cells of 140 or less [%] 87 86 64 64 70 79 Cells of 130 orless [%] 77 78 51 54 55 65 SF2 Mean 109.27 106.84 120.48 122.12 115.06116.53 Cells of 130 or less [%] 94 98 80 82 85 81 Cells of 120 or less[%] 87 97 56 56 74 72 Cells of 110 or less [%] 70 81 40 41 50 44 Celldiameter Mean [μm] 10 9 Cells of 50 μm or less [%] 100 100 Cells of 30μm or less [%] 100 99 Cells of 20 μm or less [%] 94 97 Cells of 15 μm orless [%] 79 88 Cells of 10 μm or less [%] 56 65 Number of cells/mm² 48846035 Porosity [%] 37 34 Comparative Comparative Comparative Example 1Example 2 Example 3 First Second First Second First Second observationobservation observation observation observation observation regionregion region region region region Number of cells counted 44 74 55 5451 61 Aspect ratio Mean 1.8 1.57 1.27 1.26 1.29 1.32 Cells of 1.3 orless [%] 5 30 62 67 63 66 Cells of 1.2 or less [%] 5 18 40 50 37 41Cells of 1.1 or less [%] 2 8 16 19 20 15 SF1 Mean 201.04 177.77 144.89143.26 147.94 148.43 Cells of 150 or less [%] 20 31 64 69 69 69 Cells of140 or less [%] 9 23 47 56 47 59 Cells of 130 or less [%] 5 18 38 37 3748 SF2 Mean 132.54 130.37 122.30 123.98 122.89 123.25 Cells of 130 orless [%] 61 58 75 74 76 72 Cells of 120 or less [%] 36 39 62 57 61 61Cells of 110 or less [%] 14 8 35 22 31 31 Cell diameter Mean [μm] 193160 Cells of 50 μm or less [%] 0 0 Cells of 30 μm or less [%] 0 0 Cellsof 20 μm or less [%] 0 0 Cells of 15 μm or less [%] 0 0 Cells of 10 μmor less [%] 0 0 Number of cells/mm² 16 22 Porosity [%] 47 44

(Summary of the Results)

In the case of the roller of Example 1, in each of the first and secondobservation regions, cell diameter was normally distributed around themean value (about 10 μm), and the amount of cells having an aspect ratioof 1.3 or less was found to be 87% or more. As shown in FIGS. 13 and 14,in the case of the roller of Example 1, virtually no difference wasobserved in shape factor SF1 between cells of the first observationregion and those of the second observation region, and, in each of theobservation regions, most cells exhibited an SF1 of 130 or less;specifically, an SF1 falling within a narrow range around 120 (meanvalue). Thus, the roller of Example 1 was found to have substantiallytrue spherical cells. In addition, as shown in FIGS. 25 and 26, in eachof the observation regions, most cells exhibited an SF2 (indicating tothe remoteness from complete roundness; i.e., circumferentialirregularities) falling within a narrow range of 130 or less.

Also, in the case of the roller of Example 2 or 3, in each of the firstand second observation regions, cell diameter was normally distributedaround the mean value (about 10 μm), and the amount of cells having anaspect ratio of 1.3 or less was found to be 70% or more. As shown inFIGS. 15 to 18, in the case of the roller of Example 2 or 3, virtuallyno difference was observed in shape factor SF1 between cells of thefirst observation region and those of the second observation region,and, in each of the observation regions, 80% or more of all cellsexhibited an SF1 falling within a narrow range of 150 or less. Thus, theroller of Example 2 or 3 was found to have substantially true sphericalcells. In addition, as shown in FIGS. 27 to 30, in each of theobservation regions, 80% or more of all cells exhibited an SF2(indicating to the remoteness from complete roundness; i.e.,circumferential irregularities) of 130 or less.

In contrast, in the case of the roller of Comparative Example 1, theamount of cells having an aspect ratio of 1.3 or less was found to besmall; i.e., large amounts of cells were found to be in a flattenedspherical form. As shown in FIGS. 19 and 20, in the case of the rollerof Comparative Example 1, considerably large amounts of cells exhibitedhigh SF1, and cells of different SF1 values were distributed in each ofthe first and second observation regions. Thus, the roller ofComparative Example 1 was found to have non-uniform and considerablyflattened cells. In addition, as shown in FIGS. 31 and 32, in the caseof the roller of Comparative Example 1, cells of different shape factorSF2 values were distributed in each of the observation regions, andlarge amounts of cells exhibited high SF2, as compared with the cases ofExamples 1 to 3. Thus, the roller of Comparative Example 1 was alsofound to have non-uniform and distorted spherical cells.

In the case of the roller of Comparative Example 2 or 3, the amount ofcells having an aspect ratio of 1.3 or less was found to be small (62 to67%); i.e., the amount of cells having a flattened spherical form wasfound to be large, as compared with the cases of Examples 1 to 3. Asshown in FIGS. 21 to 24, in the case of the roller of ComparativeExample 2 or 3, large amounts of cells exhibited high SF1 (i.e., 60 to70% of all cells exhibited an SF1 of 150 or less), and cells ofdifferent SF1 values were distributed in each of the first and secondobservation regions. Thus, the roller of Comparative Example 2 or 3 wasfound to have non-uniform and considerably flattened cells. In addition,as shown in FIGS. 33 to 36, in the case of the roller of ComparativeExample 2 or 3, cells of different shape factor SF2 values weredistributed in each of the observation regions, and large amounts ofcells exhibited high SF2 (i.e., 70 to 80% of all cells exhibited an SF2of 130 or less), as compared with the cases of Examples 1 to 3. Thus,the roller of Comparative Example 2 or 3 was also found to havenon-uniform and distorted spherical cells.

In the roller of Example 1, the amount of cells having a diameter of 50μm or less was found to be 100%, and the number of cells/mm² was foundto be 4,884 or more. In contrast, in the roller of Comparative Example1, the amount of cells having a diameter of 50 μm or less was found tobe 0%, and the number of cells/mm² was found to be 22 or less. Thesedata indicate that, in the roller of Example 1, very fine cells aredensely distributed, as compared with the roller of Comparative Example1.

Test Example 3

A durability test was carried out by using a belt fixing apparatus 10 asshown in FIG. 37, which includes a fixing roller 21, a pressure roller22, a heating roller 23, and a fixing belt 25. In the belt fixingapparatus 10, the fixing roller 21 is rotatably supported by a shaft;the pressure roller 22 is rotatably supported below the roller 21 sothat the roller 22 abuts the roller 21; and the heating roller 23 isrotatably supported generally above the roller 21. A heat source 24 isprovided in the interior of the heating roller 23, and the fixing belt(endless heat transfer belt) 25 is wound around the heating roller 23and the fixing roller 21.

Each of the rollers of Examples 1 to 3 and Comparative Examples 1 to 3was applied, as the fixing roller, to the belt fixing apparatus 10, andthe time elapsed until the fixing roller was broken was measured. Therewas employed, as the pressure roller 22, a roller prepared by covering asilicone sponge (φ: 35 mm, thickness: 2.5 mm, hardness (Asker C): 68°)with a PFA tube (thickness: 30 μm). The nip width was adjusted to 10.5to 11.5 mm. The durability test was carried out under the followingconditions: belt surface (heated to 160 to 170° C.), and continuousoperation (8 hours/day under heating, and 16 hours/day with turning offthe heat source (heater)). For each type of roller, the durability testwas carried out five times. Upon the durability test, the warm-up timeof each roller was measured, and the ratio of the warm-up time of theroller to that of the roller of Comparative Example 1 was determined. Asused herein, “warm-up time” refers to the rise time in a standby state.The results are shown in Table 2.

TABLE 2 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex. 2 Ex. 3 Warm-upAverage of five 1.01 1.01 1.01 1 1.01 1.01 time ratio measurementsEndurance 1 576 623 506 120 360 325 time 2 624 594 516 96 384 358 3 528542 555 48 408 316 4 572 528 574 48 432 371 5 534 556 522 24 228 321

(Summary of the Results)

As shown in Table 2, the warm-up time of each of the rollers of Examples1 to 3 and Comparative Examples 2 and 3 was almost equal to that of theroller of Comparative Example 1. These data indicate that the rollers ofExamples 1 to 3 exhibit heat insulation property comparable to that of aconventional sponge roller.

As is clear from Table 2, each of the rollers of Examples 1 to 3 can becontinuously operated for 500 hours or longer, and, in contrast, theroller of Comparative Example 1 may be generally broken throughoperation for 100 hours or shorter, and the roller of ComparativeExample 2 or 3 may be broken through operation for about 300 hours.These data indicate that the rollers of Examples 1 to 3 exhibitdurability higher than that of the rollers of Comparative Examples 1 to3 (i.e., conventional rollers).

1-18. (canceled)
 19. An elastomer porous material, characterized inthat, when cells in a first observation region of a first cross sectionare observed at a certain magnification, cells having an aspect ratioa/b, wherein a represents the maximum diameter of each cell and brepresents the length of the minor axis of that cell as measured in adirection orthogonal thereto, of 1.3 or less account for 70% or more ofall cells in the first observation region, and, when cells in a secondobservation region of a second cross section orthogonal to the firstcross section are observed at a certain magnification, cells having anaspect ratio a/b, wherein a represents the maximum diameter of each celland b represents the length of the minor axis of that cell as measuredin a direction orthogonal thereto, of 1.3 or less account for 70% ormore of all cells in the second observation region.
 20. An elastomerporous material according to claim 19, which is produced from anemulsion composition comprising, as a continuous phase, a liquid rubbermaterial which forms an elastomer through curing.
 21. An elastomerporous material according to claim 20, wherein the liquid rubbermaterial is a liquid silicone rubber material.
 22. An elastomer porousmaterial according to claim 19, wherein, in the first or secondobservation region, cells having a diameter of 50 μm or less account for50% or more of all cells.
 23. An elastomer porous material according toclaim 19, wherein, in each of the first and second observation regions,cells having a shape factor SF1, which indicates the roundness of acircle and is represented by the following formula: $\begin{matrix}{{{SF}\; 1} = {\frac{\pi \; a^{2}}{4\; A} \times 100}} & \lbrack{F1}\rbrack\end{matrix}$ (wherein a represents the length of major axis of eachcell, and A represents the area thereof), of 150 or less account for 80%or more of all cells.
 24. An elastomer porous material according toclaim 19, wherein, in the first observation region, cells having a shapefactor SF2, which indicates the remoteness from complete roundness andis represented by the following formula: $\begin{matrix}{{{SF}\; 2} = {\frac{P^{2}}{4\pi \; A} \times 100}} & \lbrack{F2}\rbrack\end{matrix}$ (wherein A represents the area of each cell, and Prepresents the perimeter length thereof), of 130 or less account for 80%or more of all cells.
 25. An elastomer porous material according toclaim 19, wherein, in the second observation region, cells having ashape factor SF2, which indicates the remoteness from complete roundnessand is represented by the following formula: $\begin{matrix}{{{SF}\; 2} = {\frac{P^{2}}{4\pi \; A} \times 100}} & \lbrack{F3}\rbrack\end{matrix}$ (wherein A represents the area of each cell, and Prepresents the perimeter length thereof), of 130 or less account for 80%or more of all cells.
 26. An elastomer porous material according toclaim 19, which exhibits a porosity of 30% or more and has 200 or morecells per mm² as observed in a cross section.
 27. A roll membercharacterized by comprising the elastomer porous material as recited inclaim
 19. 28. A fixing member characterized by comprising the elastomerporous material as recited in claim
 19. 29. A method for producing anelastomer porous material, characterized in that the method comprisespreparing, under reduced pressure, an emulsion composition comprising,as a continuous phase, a liquid rubber material which forms an elastomerthrough curing; and curing the emulsion composition while removing adispersion phase, to thereby produce an elastomer porous material.
 30. Amethod for producing an elastomer porous material production methodaccording to claim 29, wherein the liquid rubber material is a liquidsilicone rubber material.
 31. A method for producing an elastomer porousmaterial production method according to claim 29, wherein the emulsioncomposition is a water-in-oil emulsion composition comprising a liquidsilicone rubber material, a silicone oil material having interfacialactivity, and water.
 32. A method for producing an elastomer porousmaterial production method according to claim 29, which produces anelastomer porous material wherein, when cells in a first observationregion of a first cross section are observed at a certain magnification,cells having an aspect ratio a/b, wherein a represents the maximumdiameter of each cell and b represents the length of the minor axis ofthat cell as measured in a direction orthogonal thereto, of 1.3 or lessaccount for 70% or more of all cells in the first observation region,and, when cells in a second observation region of a second cross sectionorthogonal to the first cross section are observed at a certainmagnification, cells having an aspect ratio a/b, wherein a representsthe maximum diameter of each cell and b represents the length of theminor axis of that cell as measured in a direction orthogonal thereto,of 1.3 or less account for 70% or more of all cells in the secondobservation region.
 33. A method for producing an elastomer porousmaterial production method according to claim 29, which produces anelastomer porous material wherein, in the first or second observationregion, cells having a diameter of 50 μm or less account for 50% or moreof all cells.
 34. A method for producing an elastomer porous materialproduction method according to claim 29, which produces an elastomerporous material wherein, in each of the first and second observationregions, cells having a shape factor SF1, which indicates the roundnessof a circle and is represented by the following formula: $\begin{matrix}{{{SF}\; 1} = {\frac{\pi \; a^{2}}{4\; A} \times 100}} & \lbrack{F4}\rbrack\end{matrix}$ (wherein a represents the length of major axis of eachcell, and A represents the area thereof), of 150 or less account for 80%or more of all cells.
 35. A method for producing an elastomer porousmaterial production method according to claim 29, which produces anelastomer porous material wherein, in the first observation region,cells having a shape factor SF2, which indicates the remoteness fromcomplete roundness and is represented by the following formula:$\begin{matrix}{{{SF}\; 2} = {\frac{P^{2}}{4\pi \; A} \times 100}} & \lbrack{F5}\rbrack\end{matrix}$ (wherein A represents the area of each cell, and Prepresents the perimeter length thereof), of 130 or less account for 80%or more of all cells.
 36. A method for producing an elastomer porousmaterial production method according to claim 29, which produces anelastomer porous material wherein, in the second observation region,cells having a shape factor SF2, which indicates the remoteness fromcomplete roundness and is represented by the following formula:$\begin{matrix}{{{SF}\; 2} = {\frac{P^{2}}{4\pi \; A} \times 100}} & \lbrack{F6}\rbrack\end{matrix}$ (wherein A represents the area each cell, and P representsthe perimeter length thereof), of 130 or less account for 80% or more ofall cells.